Z-90 activates in July and December if an infected file is executed and the time is exactly 09:03. At this time the virus encrypts the DOS boot sector of drive C:, making the PC unbootable (encryption is done by XORing with 16-bit hex value 0903). After this it displays this message:
VIRUS Z-90. JUNIO 95. M EXICOSE MURIO TU DISCO DUROTU LO PUEDES RE VIVIRHAS BAILADO ALGUNA VEZ CON TU NOVIA A LE TENUE LUZ DE LA
Z-90 was found in the wild in Brazil in April 1996.
Once detected, the F-Secure security product will automatically disinfect the suspect file by either deleting it or renaming it.
Description Created: Peter Szor, F-Secure, 1996